1. Field of the Invention
The present invention relates to a light source device in which a filter that blocks light containing unwanted heat in an illumination light emitted from a light source lamp is provided in a rotary plate.
2. Description of the Related Art
Conventionally, an endoscope is used for observing an alimentary tract such as the esophagus, the stomach, the small intestine or the large intestine, or for observing tracheae such as the lungs by inserting an elongated insertion portion into the body. An endoscope also makes it possible to perform various kinds of examinations or curative treatments by passing a treatment instrument through a treatment instrument channel provided in the insertion portion of the endoscope.
When performing an examination, tissue extraction, treatment or the like using an endoscope, a light source device that supplies an illumination light, a control device such as a video processor that generates video signals from optical images of an examination site that are picked up by the endoscope, and a display device that displays endoscopic images of the examination site and the like are used as peripheral endoscopic devices.
In recent years, when performing diagnosis using an endoscope, in addition to normal light observation by white light in which color images of an observation site are displayed on a display device and observed, special light observation is performed that employs fluorescence, infrared light, narrow-band light (also described as “NBI”), and the like as illumination light.
Therefore, for a light source device, to enable the supply of illumination light for normal light observation and illumination light for special light observation, a configuration is adopted in which a plurality of kinds of filters are switchingly disposed in the illumination light path. Further, in the light source device, in order to block the supply of, for example, infrared light that is an unwanted heat source included in the illumination light, an infrared light cutting filter (reflective filter) that blocks infrared light is provided in the illumination light path. However, by providing an infrared light cutting filter in the illumination light path, infrared light that is reflected by the infrared light cutting filter returns to the lamp and increases the electrode temperature of the lamp, and therefore affects the life of the lamp.
Japanese Patent Application Laid-Open Publication No. 8-24219 discloses an endoscope apparatus that, as a first object, can prevent thermal damage of an endoscope that is caused by heat from the light of a lamp regardless of the capacity of the individual lamp. Further, as a second object, the endoscope apparatus can manage information regarding changes over time in the amount of light of a lamp to precisely ascertain an abnormal situation of the lamp.
In that endoscope apparatus, an infrared light cutting filter is arranged so as to reflect infrared light of a predetermined wavelength among incident light from the lamp to outside of the illumination light path and allow light other than infrared light to pass through as it is. Infrared light that is reflected light which is reflected by the infrared light cutting filter is caused to be incident on a sensor so that the intensity of the reflected light is constantly detected by the sensor.
Accordingly, by disposing the infrared light cutting filter in an inclined state with respect to the illumination light path, infrared light among the incident light from the lamp is reflected to outside the illumination light path to thereby solve the problem of deterioration of the lamp that is caused by reflected infrared light returning to the lamp.